Ion microprobe u pb dating of apatite

U th he dating of apatite a potential thermochronometer

., amelin, 2000], our in‐situ analyses could provide the following advantages in comparison with conventional tims methods: (1) a much smaller amount of sample (even thin section) is available, (2) the mineralogy of the phosphates and textural relationships with other minerals can be investigated in their natural surrounding, (3) u‐pb systematics in various phases are independently investigated. therefore, the u‐pb system of eet 87521 is not completely identical to that of eet 96008., 1999a, 1999b; warren and ulff‐møller, 1999; mikouchi, 1999; nishiizumi et al. open figuredownload powerpoint slidethe results of three‐dimensional linear regressions of eet 87521 phosphates in 238u/206pb ‐ 207pb/206pb – 204pb/206pb 3d space. the total pb/u isochron age of 3531 ± 110 ma (95% confidence limit; mswd = 2. this result is within error of the obtained pb‐pb age of 3503 ± 140 ma for phosphate, implying that the relative sensitivity factor of u+/pb+ for whitlockite is similar to that of apatite within the analytical uncertainties.

Ion microprobe u pb dating of apatite

, 2003; terada and sano, 2004], some ordinary chondrites [terada and sano, 2002, 2003] and some lunar meteorites [anand et al., 2003, figure 1] indicates that the highland components in yq‐meteorites is much more dominant than that for eet‐meteorites., ppm238u/206pb207pb/206pb204pb/206pba uncertainties assigned to the isotopic and elemental ratio are 1σ estimated by counting statistics and calibration. in spite of their scientific interest, chronological studies of very‐low‐ti (vlt) basaltic meteorites are not well understood, since most vlt basaltic meteorites are brecciated and consist of mixtures of materials with different origins. open figuredownload powerpoint slidean inverse pb/pb isochron diagram (top) for apatites and whitlockites and an inverse u/pb isochron diagram (bottom) for apatites in eet 87521. the primary purpose of the present work was to investigate the u‐pb systematics of phosphates in eet 87521, whose radiometric age has not been determined.

  • U th pb dating of phosphate minerals

    thus, all of the evidence indicates that the observed age of ∼3. ga and that a disturbance to the u‐pb system occurred at ∼4. in this study, the younger age of 100 ± 130 ma recorded in eet 96008, which might be attributable to shock metamorphism [anand et al. u concentrations and 238u/206pb, 207pb/206pb, and 204pb/206pb ratios in phosphates for eet 87521agrain no. our in‐situ analyses using the sensitive high resolution ion microprobe (shrimp) installed at hiroshima university attain high sensitivity at high mass resolution of ∼5800 [sano et al. this in‐situ u/pb dating method has been successfully applied to extraterrestrial phosphates in some martian meteorites [sano et al.
  • Ion microprobe U-Pb dating and REE analysis of apatite from

    these features are similar to the previous report for the thin section #87521‐9 [warren and kallemeyn, 1989]. in contrast, low‐ti mare basalt samples are generally younger; they range in age from 3. thus, the previously reported ages of yamato 793274 and que 94281 are apparently different from those of eet 87521 (this work) and eet 96008 [anand et al. these young gas retention ages might have been affected by the shock event when the meteorite was launched to the earth.), which is determined as an intersection with the concordia line on the 238u/206pb ‐ 207pb/206pb plane. based on the available data of vlt basalts, nyquist et al.
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  • Ion microprobe U-Pb dating of phosphates in lunar basaltic breccia

    polnau and eugster [1998] reported a k‐ar age of 3770 ma for que 94281. here, it is noted that the observed pb/pb ratios are not affected by the matrix effect of mineral species. the areas of the grains selected for shrimp analysis were free from inclusions or cracks. this technique also allows for rapid analysis of small amounts of samples (even in thin sections), and will be useful for chronological studies of samples returned from the moon, mars and asteroids in the near future. comparison with other mare basalts[10] chronological studies of numerous samples of mare basalt and related pyroclastic deposits have been well documented (for summary, see nyquist and shih, 1992; nyquist et al. experimental details of the u‐pb analysis and the calibration of the data are given by sano et al.
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Ion microprobe U–Pb dating of apatite

Ion microprobe U-Pb dating of a dinosaur tooth

the abundance ratios of 238u to 206pb for apatites were obtained from the observed 238u+/206pb+ ratios using an empirical quadratic relationship between the 206pb+/238u+ and 238u16o+/238u+ ratios of standard apatite derived from an alkaline rock of the prairie lake circular complex in the canadian shield (1156 ± 45 ma (2σ) [sano et al. thus, our result clearly indicates that the vlt basalt volcanism appears to have been prolonged on the moon (about 7 × 108 years from 3.[5] an ∼1 na o2− primary beam with acceleration voltage of 10 kv was focused to sputter an area ∼10 μm in diameter on the phosphates and positive secondary ions were extracted. this evidence questions the validities of bulk age analyses for the yamato & que meteorites in the literature and/or the hypothesis of a single‐crater origin. the thin section shows cataclastic texture, including mm‐size rock fragments with subophitic texture and/or finer matrix made of mineral fragments.; error correlation = 0), indicating that the u‐pb systems are apparently concordant within the huge uncertainties.

Ion microprobe U-Pb dating of Zagami phosphates Y. Sano1, M

b it should be noted that these 238u/206pb ratios of whitlockites are calculated assuming the relative sensitivity factor for u+/pb+ for whitlockite is the same as for apatite. the mass resolution was set to 5800 at 208pb for u‐pb analyses. the second purpose was to compare the data with the reported ages of other vlt mare basalt meteorites, which have been proposed to have been launched by a single impact event [arai and warren, 1999; warren and ulff‐møller, 1999; korotev et al. day for valuable comments about the early version of the manuscript. this study is partly supported by the supporters' association of hiroshima university and the scientific research grant of the ministry of education, culture, sports, science and technology (no.. results[6] we first calculated the “conventional” 204pb/206pb ‐ 204pb/206pb isochron age and 238u/206pb ‐ 207pb/206pb isochron age using the york methods [york, 1969] under the assumption that all phosphates were formed at the same time.

Ion microprobe U-Pb dating of a single apatite grain in meteorites

Ion microprobe U-Th-Pb dating of phosphates in martian meteorite

the observed pb‐pb age of phosphates in eet87521 is 3503 ± 140 ma, which is distinct from the results from previous chronological studies on vlt mare basalt of 3. hbr leaching and u‐pb measurements, and concluded that the yamato 793274 clast formed at ∼4. continuing to browse this site you agree to us using cookies as described in about cookies notice: wiley online library will be unavailable on saturday 25th march from 07:00 gmt / 03:00 edt / 15:00 sgt for 4 hours for essential maintenance. a k‐ar age of a bulk sample is not enough information on the formation ages of brecciated meteorites because they are admixtures of mare basalt and some highland components with different formation ages. [2001] have previously stated the similar conclusion based on a combination of the age of luna 24 vlt basalts and that of asuka lunar meteorite 881757 (3. the pb isotopic compositions have not been corrected for initial pb.

Ion microprobe U-Pb dating and strontium isotope analysis of

U–Pb and Th–Pb dating of apatite by LA-ICPMS

[2003] thoroughly investigated the chemical composition of these meteorites, and also suggested that there are not significant impediments to the hypothesis that they were launched by a single event. uncertainties of concentration are ±30% estimated by repeated measurements of standard apatite, prap. figure 2 shows the three‐dimensional linear regression for the total pb/u isochron, projected onto the 238u/206pb ‐ 207pb/206pb plane. introduction[2] the lunar meteorites are valuable sources for understanding the origin and evolution of the moon, as they potentially provide a new insight into the thermal history of unexplored regions of the moon. an inverse 207pb/206pb isochron for apatites and whitlockites and an inverse 238u/206pb isochron are shown in figures 1a and 1b, respectively. in this paper, we report ion microprobe u‐pb isotopic analyses of the brecciated lunar meteorite elephant moraine 87521 (hereafter abbreviated as eet 87521), which has been identified as a fragmental breccia predominantly consisting of vlt basaltic clasts, and which also contains a small component of highland‐derived materials [e.

In-Situ U–Pb Dating of Apatite by Hiroshima-SHRIMP: Contributions

the pb/pb isochron ages of apatite (3530 ± 270 ma) and whitlockites (3519 ± 100 ma) for eet 96008 are consistent with those of eet 87521 (3503 ± 140 ma) presented here. [2001] have suggested that the formation age of vlt mare basalt for luna 24 is 3. ga based on the bulk concentration of 40ar and the k contents. for better understanding of the thermal history for these basaltic breccias containing some highland components, detailed investigations using in‐situ dating of phosphates, which are more resistant to secondary thermal processes, will be required in the future.[11] based on the similar launching ages in addition to many textural and mineralogical similarities, arai and warren [1999] and warren and ulff‐møller [1999] proposed that yamato 793274, yamato 981031, que 94281, eet 87521 and eet 96008, which are vlt mare basalt brecciated meteorites, were launched from the moon by a single impact event. although it remains unclear whether the relative sensitivity factor of u+/pb+ for whitlockite is the same as that for apatite, the upper intercept age of 3569 ± 100 ma for eet 96008 agrees well with 3531 ± 110 ma for eet 87521.

[12] in summary, ion microprobe u‐pb dating of phosphates in lunar basaltic breccia eet 87521 were successfully carried out., 2003], we also calculated a “total pb/u isochron age” from the linear regression line in the 238u/206pb‐207pb/206pb‐204pb/206pb 3d space [wendt, 1984, 1989; ludwig, 2001], assuming that the relative u+/pb+ sensitivity factor for whitlockite is the same as that for apatite and that the u‐pb systems are concordant. analyses of three whitlockites and five apatites give a 207pb/206pb age of 3503 ± 140 ma (95% confidence limit; mswd = 0. to old article view go to article navigation abstract[1] we report ion microprobe u‐pb dating of phosphates in lunar meteorite “elephant moraine 87521 (eet87521),” which is a fragmental breccia consisting of very‐low ti (vlt) basaltic clasts and a small component of highland‐derived materials. these fragments mainly consist of plagioclase and clinopyroxene including pigeonite. the observed u/pb and pb/pb ratios for eet 96008 were well presented by planar regression rather than linear regression in 238u/206pb ‐ 207pb/206pb ‐ 204pb/206pb 3d space, and the best‐fitted planar regression intercepts the concordia curve on the 238u/206pb ‐ 207pb/206pb plane at 3569 ± 100 ma and 100 ± 130 ma (2σ).

Ion microprobe U-Pb dating and REE analysis of apatite from

eet 87521 is a polymict fragmental breccia, although it is predominantly a single lithology (or a single group of closely‐related lithologies).. u/pb ages and systematics of eet 87521 and paired eet 96008[8] so far, the age of eet 87521 has not been well documented. the solid curve is an evolution line of the u‐pb system without initial lead (concordia line), and the line is the projected regression line onto the 238u/206pb ‐ 207pb/206pb plane. analysis of five apatites and three whitlockites indicate a total pb/u isochron age of 3531 ± 110 ma (95% confidence limit; mswd = 2. this suggests that the vlt basalt volcanism appears to have been prolonged on the moon.. sample and analytical methods[3] the eet 87521 sample used in this study was a polished thin section of #87521‐4, allocated by nasa‐jsc.

Ion microprobe U-Pb dating of phosphates in lunar basaltic breccia

, 1999; eugster and terribilini, 1999], were also investigated by shrimp methods [anand et al. if this is the case, the chemical leaching of bulk samples to obtain an u‐pb age of yq‐meteorites might tend to lead to an “apparently” older age because the typical highland components often show older ages than those of typical mare basalts. the data for three whitlockites and five apatites are projected onto the 238u/206pb ‐ 207pb/206pb plane. observed 238u/206pb, 207pb/206pb and 204pb/206pb ratios of phosphates are listed in table 1. although the isotopic compositions of initial lead for the phosphates (206pb/204pb = 66 ± 99 and 207pb/204pb = 34 ± 81 at 95% confidence limit) can also be obtained from the intersection of the regression line with the 207pb/206pb‐204pb/206pb plane in the 3‐d correlation diagram, there are no additional constraints to the pb‐evolution model from these values because of the large uncertainties. apatite analyses alone give a 238u/206pb age of 4325 ± 930 ma (95% confidence limit; mswd = 0.

How long should pre dating last

ga, although some exceptions exist (the aluminous low‐ti mare basalts have ages of 3. [1996] reported a k‐ar age of 3300 ma (without analytical uncertainties), which is slightly younger than the eet 87521 phosphate formation of 3503 ± 140 ma found in this work. [1996] claimed that asuka 881757 should be classified into low‐ti mare basalt not into vlt because their bulk tio2 concentration ranges from 1.[9] the u‐pb systematics of phosphate in eet 96008, which is considered to be paired with eet 87521 [snyder et al. although the recent high‐precision thermal ionization mass spectrometry analyses enable the u‐pb dating from ∼10 microgram phosphates [e. ga for eet 87521 phosphates is distinct from vlt mare basalt for luna 24.